This invention relates generally to the repair of airfoil components used in gas turbine engines and more particularly to methods and apparatuses for correcting airfoil twist in such components.
A gas turbine engine operates according to well known principles wherein an incoming stream of atmospheric air flows through the engine along an axial flow path. A portion of the incoming air is compressed in a compressor section of the engine and then mixed with fuel and burned in a combustor section to produce a high energy, high temperature gas stream. The hot gas stream exits the combustor and subsequently passes through a turbine section that extracts energy from the hot gas stream to power the compressor and provide useful work such as powering an aircraft in flight. The compressor and turbine sections each typically include a plurality of stator vanes and rotor blades having airfoils that interact with the gas flow. The airfoils are designed to a precise shape and contour to optimize engine performance. The airfoil contour usually includes a twist from root to tip to maximize aerodynamic efficiency.
The airfoil components, as well as other components of the engine, are exposed to conditions during engine operation that limit their effective service life. These components are subjected to vibratory stresses and high temperatures and can thus become fatigued, cracked, corroded and otherwise damaged over time such that they must be either repaired or replaced to maintain safe, efficient engine operation. Airfoil components can also lose their twist because of inherent elastic loads and (in the case of rotor blades) centrifugal loads generated by rotor rotation.
Because airfoil components are relatively expensive, it is generally more desirable to repair them whenever possible. Thus, airfoil components are routinely inspected for maintenance purposes, and a wide variety of repair processes have been developed. When airfoil components are brought into a repair shop, it is often necessary to correct the airfoil twist in addition to any other repairs that are to be made. Currently, correction of twist is accomplished by holding the airfoil component in a twisting fixture and applying force to twist the component. The airfoil twist angle is then manually measured after each twist, and this process is repeated until the correct twist angle is obtained. Because the user can only estimate how much force to apply each time, this approach often requires many iterations to achieve the desired twist angle. This results in a time-consuming, labor-intensive and costly process. This approach can also result in over-twist due to applying excessive force.
Accordingly, it would be desirable to have a more accurate, more productive approach to correcting twist in airfoil components.
The above-mentioned need is met by the present invention, which provides a system for correcting twist in airfoil components. The system includes a first fixture assembly for holding a first end of an airfoil component and a second fixture assembly for holding a second end of the airfoil component. A rotary drive unit is provided for rotating the first fixture assembly. A gage is included for measuring twist angle in the airfoil component, and a controller controls the rotary drive unit in response to input from the gage to twist the airfoil component. In operation, the airfoil component""s twist angle measured by the gage is fed to the controller. The controller computes how much the airfoil component needs to be twisted to achieve a desired twist angle, and the first fixture assembly is then rotated sufficiently to twist the airfoil component to the desired twist angle.
The present invention and its advantages over the prior art will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings.